Vertical lift tubes have been implemented to enhance the heat transfer between a central fluidized bed combustor and an annular fluidized bed reactor. The increase in heat transfer resulting from the use of lift tubes has been characterized and successfully correlated with the hydrodynamics of the gas-solid flow within the lift tubes. The increase is maximized at the beginning of the transition between dense and dilute phase transport. Pressure signals at various locations in the lift tube and at its inlet have been analyzed to identify the transition point. The beginning of the transition can be identified using Fourier and Haar wavelet power spectral analysis. These conclusions have been confirmed with video analysis. By using this analysis on the pressure signals in industrial applications, the heat transfer increase from the lift tubes can be optimized. (C) 2009 Elsevier B.V. All rights reserved.